A metal silicide is a compound formed by thermal reaction (Silicidation) of silicon (Si) and a metal. A metal silicide has an intermediate resistance between those of a metal and polysilicon. Therefore, a metal silicide is used to reduce the contact resistance of the boundary of a metal and a semiconductor, or used as a conductive line material for a memory cell array. However, in Silicidation of Si and a metal, it is difficult to form a thin film of a metal silicide and to obtain a composition of low resistance. To solve this problem, a Silicidation in which metal ions are beforehand injected into Si is known. However, this method has, for example, a problem that the manufacturing process is complex, substrates will easily be damaged and the device structure is limited. Therefore, there is a demand for a Silicidation technique of simplifying the manufacturing process, and free from substrate damage and device structure limitation.